KR20040099527A - Method and apparatus for controlling track seek servo reflecting variation of acceleration in disk drive - Google Patents

Abstract

PURPOSE: A track seek servo control method and a device of a disk drive, considering an acceleration change are provided to move a transducer to a target track by using an acceleration locus of a function where an acceleration change becomes 0 in track seek start and end parts during a track seek control, thereby shortening a track seek time while reducing mechanical vibration and noise. CONSTITUTION: A seek locus generator(60) operates a design position value, a design speed value, and a design acceleration value. A state estimator(62) determines a substantial position value, a substantial speed value, and an acceleration value. The first adder(64) subtracts the substantial position value from the design position value, and outputs the subtracted result. A position control gain compensator(66) multiplies the outputted result by a position gain, and generates a position compensation value. The second adder(68) subtracts the substantial speed value from the design speed value to output the subtracted result. A speed control gain compensator(70) generates a speed compensation value. The third adder(72) subtracts the substantial acceleration value from an added value of the speed compensation value and the design acceleration value, and generates an acceleration compensation value. An actuator(76) varies a current supplied to a voice coil.

Description

Method and apparatus for controlling track seek servo reflecting variation of acceleration in disk drive}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling a disk drive, and more particularly, to a method and apparatus for controlling a track search servo of a disk drive in consideration of an acceleration change for shortening track search time while reducing noise in the disk drive.

Hard disk drives include a plurality of magnetic transducers capable of recording and reading information by sensing and magnetizing the magnetic field of each of a single or multiple rotating disks. This information is stored in a plurality of sectors located in the annular track. There is a track number located across each surface of the disc. The number of vertically similar tracks is sometimes called a cylinder. Therefore, each track is also defined by a cylinder number.

Each transducer is typically integrated within a slider that is incorporated into a head gimbal assembly (HGA). Each head gimbal assembly is attached to an actuator arm. The actuator arm has a voice coil located adjacent to the magnetic assembly that specifies the voice coil motor together. Hard disk drives typically include controllers and drive circuits that supply current to excite the voice coil motor. The excited voice coil motor rotates the actuator arm to move the transducers across the surface of the disk (s).

When writing or reading information, the hard disk drive is likely to execute a seek routine to move the transducer from one cylinder to another. During the seek routine, the voice coil motor is excited by a current that moves the transducers to a new cylinder position on the disk surface. The controller also executes a servo routine that ensures that the transducer moves to the correct cylinder position and to the center of the track.

It is desirable to minimize the amount of time needed to read or write information from the disc (s). Therefore, the seek routine executed by the drive must move the transducers to the new cylinder position in the shortest time. In addition, the settling time of the head gimbal assembly must be minimized in order for the transducer to quickly record or read information and to be positioned adjacent to the new cylinder at once.

In general, seek servo control was performed by applying an acceleration trajectory in the form of a square wave to move the transducer quickly to the target track. Unfortunately, square waves contain harmonics of high frequency components, which cause mechanical resonances in the head gimbal assembly to excite mechanical components or assemblies at high natural frequencies. This resulted in acoustic noise, unwanted vibrations and associated settling times due to residual vibrations. Mechanical resonances generated by the square waves of the prior art have had the problem of increasing both the stability and the total time needed to write or read information from the disc.

A technique developed to solve this problem is a seek control method using an acceleration trajectory in the form of a sinusoidal wave. The acceleration equations, velocity equations, and position equations according to Equation 1 are as follows.

Where constants represent acceleration constants, current amplitudes, and track seek times, respectively.

In the case of using the sinusoidal acceleration trajectory, the track search time is increased by about 10% compared to the case of using the square wave acceleration trajectory. In addition, even when using a sinusoidal acceleration trajectory such as Equation 1, mechanical noise and vibration are still generated due to a certain amount of Jerk generated at the beginning and the end of the track search.

Here, Jerk means the derivative (the amount of change of acceleration) which differentiated acceleration. In particular, Jerk values generated at the beginning and end of the track search cause mechanical noise and vibration.

However, when the square wave acceleration trajectory is used in the track search, the Jerk value at the beginning and the end of the search has an infinite value as shown in Equation 2.

When the square wave acceleration trajectory is used in the track search, the Jerk value at the beginning and the end of the search has the maximum value of the sine wave as shown in Equation 3.

Therefore, the seek servo using the sinusoidal acceleration trajectory according to Equation 1 has improved Jerk value compared to the case of using the square wave acceleration trajectory. However, as shown in Equation 3, the Jerk value corresponding to the maximum value of the sinusoidal wave starts and ends the track search. There was a problem that occurs in the portion still causing mechanical noise and vibration.

Further, as a technique developed to reduce the mechanical noise when executing the seek mode, there is a "positioning device for reducing the noise at the time of positioning" of JP-A-2001-325006.

The technique described in Japanese Laid-Open Patent Publication No. 2001-325006 is characterized by reducing the vibration and noise during track search by smoothing the acceleration, velocity, and position trajectory through a low pass filter. However, this has a disadvantage in that the circuit element is increased because a filter must be added, and this technique also has a problem in that mechanical noise and vibration caused by Jerk are not generated because Jerk value does not become zero at the beginning and end of the track search.

The technical problem to be solved by the present invention is to reduce the mechanical noise by minimizing the Jerk value generated at the beginning and the end of the track search in order to solve the above-mentioned problems of the disk drive in consideration of the acceleration change to shorten the track search time. A track search servo control method and apparatus are provided.

1 is a plan view of a configuration of a hard disk drive to which the present invention is applied.

2 is a circuit diagram of an electrical system for controlling a hard disk drive to which the present invention is applied.

3 is a circuit diagram of a servo control system of a hard disk drive according to the present invention.

4 illustrates an acceleration trajectory and a Jerk trajectory according to the related art.

5 illustrates a Jerk trajectory for making an acceleration trajectory in the form of acceleration / deceleration in the process of inducing the present invention.

6 (a)-(c) show acceleration, velocity, and position trajectories derived from Equation 5, respectively.

FIG. 7 illustrates an acceleration trajectory and a Jerk trajectory used for track search servo control of a disk drive in consideration of the change in acceleration according to the present invention.

FIG. 8 illustrates an acceleration trajectory used for track search servo control of a disk drive in consideration of the acceleration change according to the present invention according to the n value.

9 is a table comparing search performance between the present invention and the prior art.

In order to achieve the above technical problem, a track search servo control method of a disk drive considering an acceleration change according to the present invention is a disk drive control method, which is a function in which the amount of change in acceleration is zero at the beginning and the end of a track search in a track search mode The transducer is moved to a target track by a track search control process using an acceleration trajectory of.

In order to achieve the above technical problem, a track search servo control method of a disk drive in consideration of an acceleration change according to the present invention is a disk drive control method, wherein an acceleration amount of acceleration changes to zero at the beginning and the end of a track search in a track search mode The transducer is moved to the target track by a track search control process that applies a function current to the voice coil.

In order to achieve the above technical problem, a track search servo control apparatus for a disk drive in consideration of an acceleration change according to the present invention is a disk drive control apparatus comprising: an acceleration in which a change amount of acceleration is zero at a track search start and end portion in a track search mode; A seek trajectory generator that calculates a design position value, a design speed value, and a design acceleration value by applying an equation of the trajectory, a state estimator that determines the actual position value, the actual speed value, and the acceleration value at which the transducer moves on the disk, and the design position value. A first summer for subtracting and outputting an actual position value, a position control gain compensator for generating a position correction value by multiplying the first summer output value by a predetermined position gain for position correction, the position correction value and the design The speed value is added, and the sum value of the position correction value and the design speed value is added. A second summer for subtracting and outputting the actual speed value, a speed control gain compensator for generating a speed correction value by multiplying an output value of the second summer by a predetermined speed gain for speed correction, and the speed correction value and the A sum total of a design acceleration value and a third summer for subtracting the actual acceleration value from the sum of the speed correction value and the design acceleration value to generate an acceleration correction value and supplied to the voice coil corresponding to the acceleration correction value And an actuator for varying the current.

In order to achieve the above technical problem, a disk drive to which a track search servo control algorithm of a disk drive in consideration of an acceleration change according to the present invention is applied includes a disk for storing predetermined information, a spindle motor for rotating the disk, and information on the disk. A transducer that records and reads information from the disc, an actuator that moves the transducer across the surface of the disc, and an acceleration trajectory of a function where the amount of acceleration change is zero at the beginning and end of the track search in track search mode. And a controller for controlling the actuator to move the transducer from the current track to the target track.

In order to achieve the above technical problem, a disk drive to which a track search servo control algorithm of a disk drive in consideration of an acceleration change according to the present invention is applied includes a disk for storing predetermined information, a spindle motor for rotating the disk, and information on the disk. A voice coil that records and reads information from the disc, an actuator that moves the transducer across the surface of the disc, and the current of the acceleration function in which the amount of change in acceleration is zero at the beginning and end of the track search in track search mode. And a controller for controlling the actuator to move the transducer from the current track to the target track.

For disc drives, the purpose of track seek servos is to quickly move the head to the desired position with minimal noise and vibration. The Bang-Bang Seek Controller, which has the acceleration trajectory of the square wave, is the most advantageous for minimizing the search time, but is very weak in terms of noise and vibration. The Sinusoidal Seek Controller, which has the sinusoidal acceleration trajectory, It is advantageous in terms of noise but inefficient in terms of current usage compared to square waves. Therefore, the search time is increased by about 10%.

Both existing controllers have a Jerk that can cause mechanical vibrations and noise at the beginning and end of the track search.

The present invention is to design a new acceleration trajectory that can minimize the jerk amount generated at the beginning and end of the track search to reduce the noise and vibration and improve the search performance.

Jerk is a word that means sudden movement, and it represents the value of acceleration differentiation, that is, the amount of change in acceleration. The larger the value of Jerk, the greater the magnitude of impact force per unit time. Therefore, minimizing the Jerk values at the beginning and end of the track search can reduce mechanical vibrations and thus noise. As shown in FIG. 4, in the case of the bang bang seek controller, infinite jerks are generated, and in the case of the sinusoidal acceleration trajectory, cosine-shaped jerks are generated so that the jerks at the beginning and the end of the track search cannot be zero. Accordingly, in order to minimize the Jerk value at the beginning and the end of the track search when generating the acceleration trajectory, a Jerk equation having a sinusoidal shape as shown in Equation 4 may be used.

In order to generate the acceleration / deceleration form of the acceleration trajectory from Equation 4, it can be modified as shown in Equation 5 to create a Jerk trajectory having the form as shown in FIG.

By integrating Equation 5, the acceleration, velocity, and position trajectory as in Equation 6 can be derived, and the respective trajectories are shown in FIGS. 6 (a)-(c).

Deriving a relationship between the search time and the search distance from the position trajectory equation of Equation 6 is as shown in Equation 7.

However, when the Jerk equation of Equation 5 is used, the search performance is about 10% lower than that of the controller using the sinusoidal acceleration trajectory. This is because, as can be seen from the acceleration trajectory of FIG. 6 (a), the current is used less than the sine wave in terms of current use.

Therefore, in the present invention, the Jerk equation is modified as in Equation 8 to minimize the noise and vibration and improve the search performance.

,

,

,

Here, K _A , I _M , and T _SK represent acceleration constants, current amplitudes, and track seek times, respectively.

Equation (8) is an equation for generating an equivalent deceleration (coast) section using a constant current in the middle of the acceleration / deceleration section in the acceleration trajectory, and the magnitude of the current use varies according to the size of the equivalent deceleration section.

Next, the track search servo control apparatus of the disk drive in consideration of the acceleration change will be described.

First, a hard disk drive to which the present invention is applied will be described.

1 shows a configuration of a hard disk drive 10 to which the present invention is applied.

The drive 10 includes at least one magnetic disk 12 that is rotated by a spindle motor 14. The drive 10 also includes a transducer 16 located adjacent the surface of the disk 12.

The transducer 16 can read or write information on the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically transducer 16 is coupled to the surface of each disk 12. Although illustrated and described as a single transducer 16, it should be understood that this consists of a write transducer for magnetizing the disc 12 and a separate read transducer for sensing the magnetic field of the disc 12. Read transducers are constructed from Magneto-Resistive (MR) devices.

The transducer 16 can be integrated into the slider 20. The slider 20 is structured to create an air bearing between the transducer 16 and the surface of the disk 12. The slider 20 is coupled to the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 that specifies the voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque for rotating the actuator arm 24 relative to the bearing assembly 32. Rotation of the actuator arm 24 will move the transducer 16 across the disk 12 surface.

The information is typically stored in an annular track of the disc 12. Each track 34 generally includes a plurality of sectors. Each sector includes a data field and an identification field. The identification field is composed of a gray code identifying a sector and a track (cylinder). The transducer 16 is moved across the surface of the disc 12 to read or write information on other tracks.

Next, the operation of the electrical system of the hard disk drive will be described.

2 shows an electrical system 40 capable of controlling the hard disk drive 10. The electrical system 40 includes a controller 42 coupled to the converter 16 by a lead / right (R / W) channel circuit 44 and a pre-amp circuit 46. The controller 42 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like. The controller 42 supplies a control signal to the read / write channel 44 for reading from or writing information to the disk 12. Information is typically sent from the R / W channel to the host interface circuit 54. The host interface circuit 54 includes a buffer memory and control circuitry that allows a disk drive to interface to a system such as a personal computer.

The controller 42 is also coupled to a VCM drive circuit 48 that supplies a drive current to the voice coil 26. The controller 42 supplies a control signal to the drive circuit 48 to control the excitation of the VCM and the movement of the transducer 16.

The controller 42 is coupled to a nonvolatile memory such as a read only memory (ROM) or a flash memory device 50 and a random access memory (RAM) device 52. Memory elements 50 and 52 contain instructions and data that are used by controller 42 to execute software routines. One software routine is a seek routine that moves the transducer 16 from one track to another. The seek routine includes a server control routine to ensure that the transducer 16 is moved to the correct track. As an example, the memory device 50 may include acceleration, velocity, and position trajectory equations derived from Jerk equation, such as Equation 8, in which the amount of change in acceleration at the track search mode is zero at the track search mode. As described below, these equations are stored in the memory element 52 at the start of driving.

3 shows a track search servo control system according to the present invention consisting of hardware and software executed by controller 42. The track search servo control system allows the transducer 16 to be positioned exactly on the target track of the disk 12. Controller 42 executes a seek routine that moves the transducer from the first track to the new track located at distance X _SK from the first track. Gray codes of one or more tracks located between the new track and the first track are read by a transducer moving across the disc 16. This is used by the controller 42 to determine periodically whether the transducer 16 moves at a target speed and acceleration across the track.

The track search servo control system includes a state estimator 62 composed of software and hardware. State estimator 62 may determine the actual distance or position value at which transducer 16 is moved from the first track. This actual position value can be determined by reading the gray code of the track immediately below the transducer 16. State estimator 62 may also determine the actual velocity value and the actual acceleration value of transducer 16. The gray code can be sampled periodically as the transducer 16 moves to a new track position so that the controller 42 can accurately control the movement of the transducer 16.

The seek trajectory generator 60 applies an acceleration trajectory derived from a Jerk equation such as Equation 8 each time the converter 16 reads the gray code of the track 34 to convert the converter 16 from Equation 9 to Equation 14. Calculate the design position x _d (n), design speed v _d (n), and design acceleration a _d (n).

The first summer 64 subtracts the actual position value from the design position value. The position control gain compensator 66 generates a position correction value by multiplying the difference between the design position value calculated in the first summer 64 and the actual position value by the position gain k _p for position correction.

Next, the second summer 68 subtracts the actual speed value after adding the design speed value to the position correction value generated by the position control gain compensator 66.

Then, the speed control gain compensator 70 generates a speed correction value obtained by multiplying the difference between the design speed value calculated in the second summer 68 and the actual speed value by the speed gain k _v for speed correction.

Next, the third summer 72 adds the speed correction value and the design acceleration value, and then subtracts the actual acceleration value to generate the acceleration correction value u (n).

The acceleration correction value is amplified in the power amplifier 74 and then applied to the VCM actuator 76. Then, the VCM actuator 76 changes the current supplied to the voice coil according to the acceleration correction value amplified and input, thereby changing the acceleration of the movement of the transducer 16. Accordingly, it can be seen that the form of the acceleration trajectory and the form of the current trajectory applied to the voice coil are the same.

That is, the current applied to the voice coil has an acceleration change amount (Jerk value) of 0 at the beginning and the end of the track search in the track search mode as shown in FIG. It is an acceleration value obtained by integrating a Jerk equation including a section with a zero change amount.

Functions representing the design acceleration, velocity, and position trajectory provided to the third, second, first summers 72, 68, and 64 are described below.

The Jerk trajectory of Equation 8 used in the present invention and the acceleration trajectory derived therefrom are shown in FIG. 7. As shown in FIG. 7, the acceleration, velocity, and position equations were derived by dividing the Jerk trajectory into six sections.

For convenience of explanation, the K _A I _M value of Equation 8 is normalized to 1 to be described.

1) Start part of acceleration section (section ①)

t = 0-T _SK / n

This section is a section where the acceleration current is increased as a start section of the acceleration section. The Jerk equation j (t), the acceleration equation a (t), the velocity equation v (t) and the position equation x (t) in this section are as shown in Equation 9, respectively.

2) Coast section in the acceleration section (section ②)

t = T _SK / n-(T _SK / 2-T _SK / n)

This section is a section using constant acceleration current as the equivalent acceleration section in the acceleration section. Jerk, acceleration, velocity, and position equations in this section are represented by Equation 10, respectively.

3) End of acceleration section (section ③)

t = (T _SK / 2-T _SK / n) to T _SK / 2

This section is an end section of the acceleration section in which the acceleration current decreases. Jerk, acceleration, velocity, and position equations in this section are represented by Equation 11, respectively.

4) Start of deceleration section (section ④)

t = T _SK / 2-(T _SK / 2 + T _SK / n)

This section is a section where the deceleration current increases as the start of the deceleration section. Jerk, acceleration, velocity, and position equations in this section are represented by Equation 12, respectively.

5) Start of coast in deceleration section (section ⑤)

t = (T _SK / 2 + T _SK / n) to (T _SK -T _SK / n)

This section is a section using constant deceleration current as the equivalent acceleration section in the acceleration section. Jerk, acceleration, velocity, and position equations in this section are represented by Equation 13.

6) End of deceleration section (section ⑥)

t = (T _SK -T _SK / n) to T _SK

This section is the end of the deceleration section where the deceleration current is reduced. Jerk, acceleration, velocity, and position equations in this section are represented by Equation 14, respectively.

In the case of executing the seek servo using the acceleration trajectory as shown in FIG. 7 by applying the Jerk equation of Equation 8, the relationship between the search time and the search distance is shown in Equation 15.

Here, n is a division value of the entire search section, and should be determined as a value of 4 or more to make the acceleration / deceleration section. For the convenience of calculation, the distance of the equivalent deceleration section is determined as the n equal value of the search section, and of course, it may be determined as an arbitrary value.

It can be seen from Equation 9 that as the n value increases to 4, 8, 16, ..., the search performance is improved to -10%, 8%, 13.5%, ... compared to the sine wave.

8 shows the acceleration trajectory using the Jerk equation according to Equation 8 as the n value increases, and it can be seen that the current consumption becomes similar to the square wave acceleration trajectory as the n value increases in terms of current use.

For example, when n is 8, Jerk Sinusoidal Seek using the acceleration trajectory derived from Equation 8 is compared with Bang-Bang Seek using the square wave acceleration trajectory and Sinusoidal Seek using the sinusoidal acceleration trajectory. Was compared to the table of FIG. 9.

As can be seen in the table of Figure 9 Jerk Sinusoidal Seek according to the present invention has the effect of minimizing the mechanical vibration and noise while reducing the search time compared to the track search using the sinusoidal trajectory.

The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described.

As described above, according to the present invention, the sinusoidal wave is controlled to move the transducer to the target track by using the acceleration trajectory of the function in which the amount of change in acceleration is zero at the beginning and the end of the track search during the track search control of the disc drive. Compared to the conventional seek technique using a form of acceleration trajectory, the effect of reducing the mechanical vibration and noise while reducing the track search time is generated.

Claims (22)

In the disk drive control method, In track search mode, the track search of the disk drive considering the change of acceleration is characterized by moving the transducer to the target track by the track search control process using the acceleration trajectory of the function whose acceleration change is zero at the beginning and the end of the track search. Servo control method. The method of claim 1, wherein the acceleration trajectory has a symmetrical form of acceleration and deceleration. The method of claim 1, wherein the acceleration trajectory is designed to include a section in which the change amount of the acceleration is zero for each predetermined period in the acceleration section and the deceleration section. The method of claim 1, wherein the acceleration trajectory is as follows. , , , Where K _A , I _M , and T _SK represent acceleration constants, current amplitudes, and track seek times, respectively, and n represents the split value of the entire search interval. A track search servo control method of a disk drive considering acceleration change, which is derived from an integral function of Jerk equation j (t). In the disk drive control device, A seek trajectory generator that calculates a design position value, a design speed value, and a design acceleration value by applying an equation of an acceleration trajectory in which the amount of acceleration change is zero at the beginning and the end of the track search in the track search mode; A state estimator for determining an actual position value, an actual velocity value, and an acceleration value at which the transducer is moved on the disk; A first summer subtracting the actual position value from the design position value and outputting the subtractor; A position control gain compensator for generating a position correction value by multiplying the first summer output value by a predetermined position gain for position correction; A second summer that adds the position correction value and the design speed value and subtracts the actual speed value from the sum of the position correction value and the design speed value and outputs the subtractor; A speed control gain compensator for generating a speed correction value by multiplying an output value of the second summer by a predetermined speed gain for speed correction; A third summer that adds the speed correction value and the design acceleration value and subtracts the actual acceleration value from the sum of the speed correction value and the design acceleration value to generate an acceleration correction value; And And an actuator for varying an electric current supplied to the voice coil according to the acceleration correction value. The apparatus of claim 5, wherein the acceleration trajectory has a symmetrical form of acceleration and deceleration. The apparatus of claim 5, wherein the acceleration trajectory is designed to include a section in which the change amount of the acceleration is zero in each of the acceleration section and the deceleration section, respectively. 7. A disk for storing predetermined information; A spindle motor for rotating the disk; A converter for writing information to and reading information from the disk; An actuator for moving the transducer across the surface of the disk; And And a controller for controlling the actuator to move the transducer from the current track to the target track using the acceleration trajectory of the function in which the change in acceleration is zero at the beginning and the end of the track search in the track search mode. Disk drive. The disk drive of claim 8, wherein the acceleration trajectory has a symmetrical form of acceleration and deceleration. The disk drive of claim 8, wherein the acceleration trajectory is designed such that an acceleration change amount is set to 0 in each of the acceleration period and the deceleration period. In track seek mode, a computer readable medium having computer program code programmed to move the transducer to a target track by means of a track seek control process using an acceleration trajectory of a function where the change in acceleration is zero at the beginning and end of the track seek. Computer program product, characterized in that it comprises a. 12. The computer program product of claim 11, wherein the acceleration trajectory has a symmetrical form of magnitude of acceleration and magnitude of deceleration. 12. The computer program product according to claim 11, wherein the acceleration trajectory is designed to include a section in which the change amount of the acceleration is zero for a predetermined period in the acceleration section and the deceleration section, respectively. In the disk drive control method, In the track search mode, the disk in consideration of the acceleration change is characterized by moving the transducer to the target track by a track search control process that applies a current of the acceleration function to the voice coil at the beginning and the end of the track search. Track search servo control method of drive. 15. The method of claim 14, wherein the trajectory of the current has a symmetrical shape of an acceleration section and a magnitude of the acceleration section. 15. The method of claim 14, wherein the trajectory of the current is designed to include a coast section using a constant current for a predetermined period in the acceleration section and the deceleration section, respectively. . A disk for storing predetermined information; A spindle motor for rotating the disk; A converter for writing information to and reading information from the disk; An actuator for moving the transducer across the surface of the disk; And And a controller for controlling the actuator to move the transducer from the current track to the target track by applying a current of the acceleration function to the voice coil at the beginning and the end of the track search, where the change in acceleration is zero. Characterized by disk drive. 18. The disk drive of claim 17, wherein the trajectory of the current has a symmetrical shape of an acceleration section and a magnitude of a deceleration section. 18. The disk drive of claim 17, wherein the trajectory of the current is designed to include a coast section using a constant current for a predetermined period in each of the acceleration section and the deceleration section. A computer with computer program code programmed to move the transducer to a target track by a track search control process that applies a current of the acceleration function to the voice coil at which the change in acceleration is zero at the beginning and end of the track search in track search mode. And a computer program product comprising a readable medium. 21. The computer program product according to claim 20, wherein the trajectory of the current has a symmetrical shape between the magnitude of the acceleration period and the magnitude of the acceleration period. 21. The computer program product according to claim 20, wherein the trajectory of the current is designed to include a coast section using a constant current for a predetermined period in each of the acceleration section and the deceleration section.